COMPARISON OF NONINVASIVE APPROACHES TO RED MARROW DOSIMETRY FOR RADIOLABELED MONOCLONAL-ANTIBODIES

Red marrow is usually the dose-limiting organ during radioimmunotherapy. Several non-invasive approaches to calculate the red marrow dose have been proposed. We compared four approaches to analyse the differences in calculated red marrow doses. The data were obtained from immunoscintigraphy of two antibodies with different red marrow kinetics [iodine-131-16.88 IgM and indium-111-OV-TL-3 F(ab')(2)]. The approaches are based on, respectively, homogeneously distributed activity in the body, a red marrow-blood activity concentration ratio of 0.3, scintigraphic quantification, and a combination of the second and third approaches. This fourth approach may be more adequate because of its independence from the chosen antibody. In addition, the influence of activity accumulation in liver, kidneys or cancellous bone on red marrow dose was studied. The calculated red marrow dose varied between 0.14 and 0.42 mGy/MBq for In-111-OV-TL-3 and between 0.13 and 0.68 mGy/MBq for I-131-16.88. If the radiopharmaceutical shows high affinity for cancellous bone or another organ situated near the red marrow, the activity in these organs must be included in dose calculations. This study shows a large variation in calculated red marrow dose and selection of the definitive non-invasive approach awaits validation.</p

Identifying vulnerable carotid plaques by noninvasive imaging

Stroke results in considerable morbidity and mortality. Prevention is therefore of particular importance. On the basis of large clinical trials, carotid endarterectomy (CEA) is performed in selected patient groups to prevent stroke. Patient symptomatology and degree of carotid stenosis are the main clinical grounds to perform CEA. However, many individual patients undergo surgery with its attendant risks without taking advantage of it, whereas in others CEA is probably incorrectly withheld. There is therefore an urgent need for new adjuncts to identify high-risk subgroups of patients who particularly benefit from potentially hazardous interventions. Multiple noninvasive imaging modalities have shown their potential to differentiate high-risk, vulnerable carotid plaques from stable plaques. The ultimate goal is to implement one or a combination of these imaging modalities in daily clinical practice. This review gives an up-to-date overview of the clinical potential of these imaging modalities in identifying patients with carotid atherosclerosis who are at high risk for developing stroke. Advantages and limitations of each imaging technique are outlined. Additionally, recommendations for future research are presented

Comparison of myocardial uptake of fluorine-18-fluorodeoxyglucose imaged with PET and SPECT in dyssynergic myocardium

PET with F-18-fluorodeoxyglucose (FDG) can detect viable myocardium and predict functional recovery after revascularization. The use of PET for clinical routine, however, is limited. Recently, imaging FDG with SPECT was proposed. The aim of this study was to compare the diagnostic value of FDG-PET and FDG-SPECT in the detection of viable myocardium in segments with abnormal wall motion, Methods: Twenty patients with previous myocardial infarction were studied. All underwent FDG-PET and FDG-SPECT during hyperinsulinemic glucose clamping. Regional perfusion was assessed with N-13-ammonia PET and early resting Tl-201- SPECT. Regional wall motion was assessed with two-dimensional echocardiography, The agreement between FDG/N-13-ammonia PET and FDG/Tl-201 SPECT to detect viability in dyssynergic myocardium was 76%. On a patient basis, PET and SPECT yielded comparable results in 17 of 20 patients. In a subgroup of patients with LVEF less than or equal to 35% (n = 12), all PET and SPECT viability data were identical. Conclusion: This study shows a good correlation between the detection of viability in dyssynergic myocardium with FDG/N-13-ammonia PET and FDG/Tl-201 SPECT, both On a Segmental and patient basis